JP7333772B2 - gas laser device - Google Patents

Description

The present disclosure relates to a gas laser device using gas such as carbon dioxide gas as a laser medium.

For example, a conventional gas laser device described in Patent Document 1 is applied to a laser processing machine and emits laser light for processing a work. It is known that as the gas laser device is used continuously, the composition of the gas, which is the laser medium enclosed in the vacuum vessel, changes, and the output of the laser light emitted to the outside decreases accordingly. .

Here, the following (1) to (3) are present as factors that cause changes in the composition of the laser medium.
(1) Due to discharge, carbon dioxide gas (CO2) contained in the laser medium undergoes a divergence equilibrium reaction (2CO2 ⇔ 2CO+O2), thereby changing the composition of the laser medium.
(2) The composition of the laser medium changes due to the outgassing emitted from the parts inside the vacuum vessel that encloses the laser medium. When used under conditions of high laser light output, the power supplied from the power supply unit to the electrodes inside the vacuum vessel increases, and the temperature of the laser medium rises, so the amount of outgas emitted from the parts increases. .
(3) An O-ring is used for the hermetic sealing portion of the vacuum vessel that encloses the laser medium. A slight airtight leak exists due to fine dust being caught in the seal. The composition of the laser medium changes as external air enters from this portion.

When the composition of the laser medium changes, the output of laser light emitted to the outside decreases. If the amount of decrease in the output of the laser light becomes large and the output required for processing cannot be maintained, laser processing such as cutting, welding, and drilling cannot be performed well, resulting in defective processing. For this reason, it is necessary to periodically replace the laser medium with a new one, and the frequency of this replacement (the time from when one replacement is performed until the next replacement is required) is called the closing time. Normally, the closing time is set to a numerical value with a margin. This is a set value that assumes the worst case, because the amount of change in the composition of the laser medium varies depending on individual differences (manufacturing variation) of the gas laser device, usage conditions such as under what conditions the laser light output is used, etc. This is because it is necessary to In other words, for many users, the laser medium can be used for a longer time than the specified closing time, but the laser medium is replaced at short intervals (closing time) set assuming the worst case. However, the actual situation is that the laser medium is not used up to the limit. Also, replacing the laser medium, that is, evacuating the old laser medium from the vacuum chamber and injecting new laser medium from the gas cylinder into the vacuum chamber normally takes 30 minutes to 1 hour. You can't afford downtime. If the laser medium can be used to the limit and the replacement frequency can be reduced, downtime can be reduced.

In order to solve this problem, the gas laser apparatus disclosed in Japanese Patent Application Laid-Open No. 2002-200001 indirectly detects changes in gas purity, that is, changes in composition from the result of monitoring the pressure inside a container in which the gas is sealed, and replaces the gas. Determines whether it is necessary or not.

JP-A-7-94810 JP 2015-156444 A

The gas laser device described in Patent Document 2 determines when to replace the laser medium based on the gas pressure rise due to leakage. However, as described above, leakage is not the only factor that changes the composition of the laser medium. Furthermore, when the pressure is measured in a vacuum container with a constant volume, the pressure is affected by the temperature according to the gas equation of state (PV=nRT). That is, the higher the temperature of the gas, the higher the measured pressure proportionally. There is a great difficulty here.

Also, the temperature of the laser medium changes depending on under what conditions the output of the laser light is used. Since the laser beam output conditions vary depending on the object to be processed (material, plate thickness) and the shape to be processed, the pressure of the laser medium varies during laser processing, and the amount of leakage must be calculated by measuring the pressure. can't. Therefore, the pressure change is measured after the end of laser processing. was rising. In addition, since the temperature of the laser medium is lowered by heat radiation to the outside, the temperature of the outside atmosphere (outside air temperature) also changes the degree of temperature drop. In addition, the volume of the vacuum vessel is large, and parts such as the blower and the electrode that become hot during laser oscillation are placed inside it in a vacuum-insulated form, so the temperature of these parts and the laser medium drops. The rate of increase is very slow, and it takes a long time for the temperature of the laser medium to become the same as the ambient temperature.

Therefore, in order to accurately calculate the leak amount based on the pressure change, it is necessary to leave the laser processing for a long time before measuring. Since it is difficult for the user to stop the device for such a long time, it is difficult to practically use the technique of calculating the leak amount based on the pressure change as described in Patent Document 2.

Therefore, it is desired to realize a technique for determining the replacement timing of the laser medium with high accuracy. As described above, when the composition of the laser medium changes, the output of the laser light decreases. Therefore, it is conceivable to determine when to replace the laser medium from the decrease in the output of the laser light. However, in some cases, the output of the laser light is lowered due to factors other than the change in the composition of the laser medium. In addition to changes in the composition of the laser medium, the factors that cause a decrease in the output of laser light in a gas laser device include dust adhering to the reflecting surface of the mirror used in the process of amplifying the output of the light emitted by the light source, and external forces acting on the device. There is the occurrence of physical deviation in the optical system due to the addition of . If the output of the laser beam is reduced due to these factors, processing defects will also occur. Realization of technology that can implement countermeasures is desired.

The present disclosure has been made in view of the above, and an object of the present disclosure is to obtain a gas laser device capable of detecting multiple types of abnormalities that reduce the output of laser light.

In order to solve the above-described problems and achieve the object, the gas laser device according to the present disclosure includes a laser oscillation unit that generates laser light using gas as a laser medium, and a command output for the output of the laser light emitted from the laser oscillation unit. The first abnormality of the laser oscillation unit is determined based on the magnitude relationship between the amount of decrease from , the first threshold, the second threshold, and the third threshold, and the length of time that the magnitude relationship continues without changing. an abnormality detection unit that detects the state, the second abnormal state, and the third abnormal state. The abnormality detection unit detects a first abnormal state when a duration of a state in which the amount of decrease is greater than or equal to the first threshold and less than the second threshold exceeds a first time, and detects the first abnormal state when the amount of decrease is greater than or equal to the second threshold and less than the third A second abnormal state is detected when the duration of the state below the threshold exceeds a second time that is shorter than the first time, and the duration of the state where the amount of decrease is equal to or greater than the third threshold is shorter than the second time. When the third time has passed, a third abnormal state is detected, and when the abnormality detection unit detects the first abnormal state, the laser light emission is stopped, the laser medium is replaced, and then the laser light is emitted. is resumed, and when the abnormality detection unit detects the second abnormal state, the emission of the laser light is stopped and a message is displayed on the display unit to prompt the user to resolve the abnormality, and the abnormality detection unit detects the third abnormal state. is detected, the laser light emission is stopped, and the state is shifted to a state in which the user's operation for instructing restart is not accepted.

Advantageous Effects of Invention According to the present disclosure, it is possible to realize a gas laser device capable of detecting multiple types of abnormalities that reduce the output of laser light.

1 is a diagram showing a configuration example of a gas laser device according to a first embodiment; FIG. Cross-sectional view of a vacuum vessel provided in the gas laser apparatus shown in FIG. A diagram showing an example of how the laser light output changes as the composition of the laser medium changes. A diagram showing an example of abnormal discharge in a gas laser device A diagram showing an example of how the laser light output changes due to the occurrence of abnormal discharge. A diagram showing an example of how the laser light output changes due to the occurrence of angular deviation of the optical resonator mirrors. A diagram showing an example of how the laser light output changes due to dust sticking to the surface of the optical resonator mirror. FIG. 2 is a diagram showing a configuration example of a control device included in the gas laser device according to the first embodiment; 3 is a flow chart showing an example of the operation of the gas laser device according to the first embodiment; FIG. 2 is a diagram showing an example of hardware that implements a control device included in the gas laser device according to the first embodiment; FIG.

Gas laser devices according to embodiments of the present disclosure will be described in detail below with reference to the drawings.

Embodiment 1.
FIG. 1 is a diagram showing a configuration example of a gas laser device 100 according to a first embodiment. 2 is a cross-sectional view of the vacuum vessel 1 included in the gas laser device 100 shown in FIG. A gas laser device 100 is used, for example, in a laser processing machine (not shown), and emits a laser beam 10 toward a work.

In the gas laser device 100, each component is mounted inside a vacuum vessel 1, and a laser medium 2 is enclosed at a pressure of approximately 30 to 300 Torr. A laser medium 2 is circulated by a blower 3 from a rectifying duct 4 toward an electrode 5 as indicated by arrows. The electrodes 5 are supplied with a high voltage from a power supply unit 6 , whereby a discharge 7 is generated between the opposing electrodes 5 . Energy from the discharge 7 is applied to the laser medium 2 to excite the carbon dioxide gas that is the laser medium 2 . Photons emitted during the transition of carbon dioxide are amplified by an optical resonator mirror consisting of a partially reflecting mirror 8 and a totally reflecting mirror 9 that face each other with the laser medium 2 interposed therebetween. The laser light 10 is emitted from the mirror 8 to the outside. The laser medium 2 energized by the discharge 7 is cooled by the heat exchanger 11 due to its increased temperature. Apertures 12 are arranged between the electrode 5 and the partially reflecting mirror 8 and between the electrode 5 and the total reflecting mirror 9, respectively. These apertures 12 play a role of determining the transverse mode order and cutting diffracted light and scattered light.

A typical gas laser device has the property that the composition of the laser medium gradually changes as it is used, and the output of the emitted laser light decreases accordingly. The gas laser device 100 is also the same. Therefore, the gas laser device 100 is configured to evacuate the laser medium 2 by the vacuum pump 13 and replace it with a new laser medium 2 when the composition change of the laser medium 2 progresses. Cooling water is supplied from a cooling device 14 to the heat exchanger 11 and components that require cooling (not shown). A series of operations are controlled by the control device 15 . The vacuum vessel 1 and each component inside the vacuum vessel 1, the power supply unit 6, and the vacuum pump 13 together with an output measuring section 21, which will be described later, constitute a laser oscillation section 20. FIG.

The gas laser device 100 is configured so that a part of the laser light is transmitted through the total reflection mirror 9 and emitted to the outside. A measurement unit 21 is provided. The output measuring unit 21 calculates the output of the laser beam 10 by multiplying the value measured by the power sensor by a predetermined coefficient. The coefficient is derived from the relationship between the measured values of the output of the laser beam emitted from the total reflection mirror 9 and the output of the laser beam 10 emitted from the partial reflection mirror 8 measured in advance. A measurement result obtained by the output measuring section 21 is input to the control device 15 and the power supply unit 6 . Based on the output value of the laser light emitted by the gas laser device 100, the control device 15 detects an abnormality of the gas laser device 100, more specifically, detects a decrease in the output of the laser light 10 and identifies the cause of the output decrease. A typical gas laser device has an output measuring unit that measures the output of the laser beam actually emitted in order to control the output of the laser beam emitted to the outside to a desired value. there is The gas laser device 100 according to the present embodiment also utilizes this existing output measuring unit, thereby achieving downsizing and cost reduction of the device.

In the example shown in FIG. 1, the total reflection mirror 9 transmits a part of the laser beam to the outside, and the output of this laser beam is measured by the output measuring unit 21. However, another configuration is possible. is. Specifically, it is possible to adopt a configuration in which part of the laser light 10 emitted from the partial reflecting mirror 8 is extracted by a beam splitter or the like, and the output of the extracted laser light is measured by the output measuring unit 21. be. In this case, similarly to the above, the output measuring unit 21 calculates the output of the laser light 10 by multiplying the measured value by the power sensor by the coefficient.

Here, the abnormality detected by the control device 15 will be described.

As described above, when the composition of the laser medium 2 changes, the output of the laser light 10 decreases. The controller 15 detects when the output of the laser beam 10 is lowered due to the change in the composition of the laser medium 2 . The output of the laser light 10 in this case changes, for example, as shown in FIG.

FIG. 3 is a diagram showing an example of how the output of the laser light 10 changes as the composition of the laser medium 2 changes. In FIG. 3, the solid line indicates the commanded laser power and the dashed line indicates the detected laser power. A command laser output is a target value for the output of the laser beam 10 . The detected laser power is the value of the actual power of laser light 10 . In FIG. 3, the horizontal axis indicates time, and the vertical axis indicates output.

As shown in FIG. 3, when the output of the laser beam 10 decreases as the composition of the laser medium 2 changes, from the time the gas laser device 100 starts emitting the laser beam 10 to a certain point A, the command laser output is , the detected laser output almost follows. Normally, control is performed so that the two match. Since the composition of the laser medium 2 is constantly changing, the detected laser output should always decrease. This can be compensated for by increasing the input power. Therefore, the detected laser output almost follows the command laser output up to the capacity margin of the power supply unit 6 . However, after point A, where the capacity of the power supply unit 6 is exceeded, the commanded laser output is constant, but the detected laser output gradually decreases as the composition of the laser medium 2 changes.

Also, normally, as shown in FIGS. 1 and 2, a discharge 7 is generated between the upper and lower electrodes 5, but if the state of the laser medium 2 existing between the upper and lower electrodes 5 is poor, 5, and discharge may occur between the electrode 5 and the rectifying duct 4 like an abnormal discharge 7a shown in FIG. In this case, the surface temperature of the electrode 5 rises rapidly due to creeping discharge, and the electrode 5 breaks. The control device 15 detects the occurrence of the abnormal discharge 7a due to the poor state of the laser medium 2 as described above. The output of the laser light 10 in this case changes, for example, as shown in FIG.

FIG. 5 is a diagram showing an example of how the output of the laser beam 10 changes due to the occurrence of abnormal discharge. Similar to FIG. 3, in FIG. 5 the solid line indicates the commanded laser power and the dashed line indicates the detected laser power. The horizontal axis indicates time, and the vertical axis indicates output. It is also assumed that an abnormal discharge occurs at point B in FIG.

As shown in FIG. 5, when the output of the laser beam 10 decreases due to the occurrence of an abnormal discharge, the command laser output remains constant, but the detected laser output suddenly drops to near 0 at the point B where the abnormal discharge 7a occurs. Decrease. Since the discharge 7 is generated between the upper and lower electrodes 5 in a normal state, the optical axis along which the laser light passes (the straight line connecting the partial reflector 8 and the total reflector 9) is located between the upper and lower electrodes 5. are arranged as follows. As a result, every time reflection is repeated between the partial reflection mirror 8 and the total reflection mirror 9, excitation energy is obtained from the discharge, and the laser light is oscillated and amplified. However, in the abnormal discharge 7a, since the discharge occurs between the electrode 5 and the rectifying duct 4, even if the reflection is repeated between the partial reflection mirror 8 and the total reflection mirror 9, the excitation energy due to the discharge cannot be obtained. , almost no laser output. That is, when the abnormal discharge 7a occurs, the detected laser output drops to near zero.

The causes of deterioration of the state of the laser medium 2 are, for example, the following (1) to (4).
(1) When the laser medium 2 with the wrong gas composition is enclosed in the vacuum vessel 1 (2) When the gas cylinder is not properly connected (3) Corrosion progresses in the heat exchanger 11 and cooling water leaks into the vacuum vessel 1 (4) The oil of the vacuum pump 13 leaks into the vacuum vessel 1 If there is a backflow inside the

Since the discharge (current) flows through a route that is easy to flow, if the state of the laser medium 2 deteriorates due to the above-mentioned causes (1) to (4), discharge (current) between the upper and lower electrodes 5 (laser medium This is because the creeping discharge flowing on the surface of the electrode 5 becomes easier to flow than the air discharge crossing the electrode 2). In this case, the temperature of the electrode surface rises rapidly due to creeping discharge, and the electrode 5 breaks. Since the surface of the electrode 5 is made of a dielectric material such as glass or ceramic, the glass or ceramic breaks due to a sudden temperature rise. Specifically, when the abnormal discharge 7a described above continues for 5 seconds or more, or when the abnormal discharge 7a continues for less than 5 seconds but is repeatedly generated, the electrode 5 is broken. If the electrode 5 breaks, the glass or ceramics forming the electrode 5 will break and scatter into the vacuum vessel 1 , or the cooling water (not shown) that cools the glass or ceramics will flow into the vacuum vessel 1 . If it leaks, it will cause serious damage, and it will take a lot of money and time to restore it. Therefore, when abnormal discharge occurs, it is necessary to immediately stop the device and take measures to prevent the user from restarting the gas laser device 100 and causing repeated abnormal discharge.

Further, when force is applied to the gas laser device 100 from the outside due to an earthquake, construction work, contact, or the like, the angles of the optical resonator mirrors may shift, and the output of the laser beam 10 emitted to the outside may decrease. Specifically, when the angle of the resonator mirror shifts, the axis (optical axis) of the light passing through the center of the aperture of the aperture 12 shifts, and the light that cannot pass through the aperture of the aperture 12 shifts. will increase. The output of the laser beam 10 is reduced by the amount of light that cannot pass through the opening of the aperture 12 . The controller 15 detects when the output of the laser beam 10 is reduced due to the displacement of the optical resonator mirrors due to the application of external force. The output of the laser light 10 in this case changes, for example, as shown in FIG.

FIG. 6 is a diagram showing an example of how the output of the laser beam 10 changes due to the occurrence of angular deviation of the optical resonator mirrors. Similar to FIG. 3, in FIG. 6 the solid line indicates the commanded laser power and the dashed line indicates the detected laser power. The horizontal axis indicates time, and the vertical axis indicates output. It is also assumed that an angular deviation of the optical resonator mirror occurs at point C in FIG.

As shown in FIG. 6, when the output of the laser beam 10 decreases due to the occurrence of angular deviation of the optical resonator mirrors, the command laser output is constant, but the point at which the angular deviation of the optical resonator mirrors occurs At C, the detected laser power suddenly decreases. However, the output does not decrease to nearly 0, but a certain amount of output (output of about 70% in the example of FIG. 6) is maintained. In addition, there is a characteristic that the fluctuation range is large after the detected laser output suddenly decreases. This feature occurs for the following reasons. The optical resonator mirrors (partial reflecting mirror 8 and total reflecting mirror 9) are fixed by mirror holders (not shown). The mirror holder is irradiated. As a result, the mirror holder is thermally deformed by the laser beam, and the angle of the optical resonator mirror held by the mirror holder is further deviated, and this repeats, increasing the fluctuation range of the detected laser output.

Further, as described above, inside the vacuum vessel 1 there are various parts such as the blower 3 , the rectifying duct 4 , the electrodes 5 , the heat exchanger 11 and the aperture 12 . Each of these parts is cleaned and assembled in a clean room, but it is still not possible to completely eliminate fine dust, and fine dust adheres to each part. Processes where dust adheres include cutting powder and atmospheric dust adhering to parts during machining (cutting, etc.), and dust adhering to parts during storage. Dust floating in the air and dust on your hands adheres to parts when they are being transported. There is such a thing as adhering to Fine dust adhering to these parts is blown up by the flow of the laser medium 2 circulated by the blower 3, and when it reaches the vicinity of the surface of the partial reflector 8 or the total reflector 9, the dust becomes a laser beam. is irradiated, and the dust is burned onto the surface of the partial reflection mirror 8 or the total reflection mirror 9 (hereinafter referred to as the mirror surface). When dust is burned onto the mirror surface, the output of the laser beam 10 emitted to the outside is reduced. The control device 15 detects when the output of the laser beam 10 is lowered due to dust burning onto the mirror surface. The output of the laser light 10 in this case changes, for example, as shown in FIG.

FIG. 7 is a diagram showing an example of how the output of the laser beam 10 changes when dust sticks to the surface of the optical resonator mirror. Similar to FIG. 3, in FIG. 7 the solid line indicates the commanded laser power and the dashed line indicates the detected laser power. The horizontal axis indicates time, and the vertical axis indicates output. Also, in FIG. 7, it is assumed that dust sticking to the mirror surface occurs at point D. FIG.

As shown in FIG. 7, when the output of the laser beam 10 decreases due to the occurrence of dust burn-in on the mirror surface, the command laser output is constant, but at point D where dust burn-in occurs on the mirror surface. , the detected laser power suddenly decreases. However, the output does not decrease to nearly 0, and a certain amount of output (output of about 60% in the example of FIG. 7) is maintained. Moreover, even if it is said to be a sudden decrease, it is not a completely linear decrease as in the case where the angle of the optical resonator mirror shown in FIG. This rattling progresses as minute dust particles burn onto the mirror surface and at the same time damage occurs to the reflective coating of the mirror.

As described above, there are various reasons why the output of the laser beam 10 decreases, but the behavior of the change after the output decrease of the laser beam 10 starts is different. Therefore, by focusing on the amount of decrease (ΔP=Ps−Pk) in the detected laser output (assumed to be Pk) with respect to the command laser output (assumed to be Ps), the rate of change in the amount of decrease (ΔP), and the behavior after the decrease, which It can be determined whether an abnormality has occurred and the output of the laser beam has decreased.

Therefore, the control device 15 of the gas laser device 100 according to the present embodiment monitors the output of the laser light 10 emitted from the laser oscillator 20, and identifies which abnormality has occurred from the behavior of the output of the laser light 10. do.

FIG. 8 is a diagram showing a configuration example of the control device 15 included in the gas laser device 100 according to the first embodiment. As shown in FIG. 8, the control device 15 controls the abnormality detection section 51 for detecting an operational abnormality of the gas laser device 100, the power supply unit 6, the vacuum pump 13 and the cooling device 14, so that the laser beam 10 is emitted from the gas laser device 100. An operation control unit 52 for emitting light and a display unit 53 for displaying the content of the abnormal operation detected by the abnormality detection unit 51, the content of notification to the user, and the like are provided. The abnormality detection unit 51 detects various abnormal states described above.

That is, the abnormality detection unit 51 detects multiple kinds of abnormal states based on the output value of the laser beam 10 measured by the output measurement unit 21 shown in FIG. Further, the operation control section 52 performs a control operation according to the type of abnormal state detected by the abnormality detection section 51 .

Specifically, the abnormality detection unit 51 detects a first abnormality in which the output of the laser beam 10 is reduced due to a change in the composition of the laser medium 2, an angular deviation of the optical resonator mirror, or dust on the mirror surface. A second abnormal state in which the output of the laser beam 10 decreases due to burn-in, and a third abnormal state in which the output of the laser beam 10 decreases due to the occurrence of abnormal discharge (abnormal discharge 7a shown in FIG. 4) are detected. .

When the abnormality detection unit 51 detects the first abnormality, the operation control unit 52 performs control to stop the emission of the laser light 10 and control to replace the laser medium 2 in the vacuum vessel 1. This is done for unit 6 and vacuum pump 13 . The operation control unit 52 restarts the emission of the laser light 10 after the replacement of the laser medium 2 is completed. Further, when the second abnormal state is detected by the abnormality detection section 51, the operation control section 52 controls the power supply unit 6 to stop the emission of the laser light 10, and also displays a message prompting to eliminate the abnormality. Displayed on the display unit 53 . Further, when the abnormality detection section 51 detects the third abnormal state, the operation control section 52 controls the power supply unit 6 to stop the emission of the laser light 10 . After stopping the emission of the laser beam 10 due to the detection of the third abnormal state, the operation control unit 52 does not accept an operation to restart the gas laser device 100 from the user for device protection. That is, the state shifts to a state in which the user cannot restart the gas laser device 100 .

The abnormality detection unit 51 determines the first to third abnormal states as follows.

(Determination of first abnormal state)
As described with reference to FIG. 3, the decrease in the output of the laser light 10 due to the change in the composition of the laser medium 2 progresses gradually. That is, the speed at which the output of the laser beam 10 decreases is slow. Therefore, for example, when the command laser output Ps is 4000 [W], the abnormality detection unit 51 determines the first abnormality state when "200 [W] ≤ ΔP < 400 [W]".

(Determination of second abnormal state)
As described with reference to FIGS. 6 and 7, the decrease in the output of the laser beam 10 due to the angular misalignment of the optical resonator mirrors or the burning of dust onto the mirror surfaces is greater than that due to changes in the composition of the laser medium 2. big. That is, the speed at which the output of the laser beam 10 decreases is fast. However, rather than the value decreasing to near zero, some output value is maintained. Therefore, for example, when the command laser output Ps is 4000 [W], the abnormality detection unit 51 determines the second abnormal state when "400 [W]≤ΔP<3200 [W]".

(Determination of third abnormal state)
As described with reference to FIG. 5, when the output of the laser beam 10 decreases due to the occurrence of an abnormal discharge, the output of the laser beam 10 rapidly decreases as in the second abnormal state, but the output value remains 0. decrease to near Therefore, for example, when the command laser output Ps is 4000 [W], the abnormality detection unit 51 determines the third abnormality state when "3200 [W]≤ΔP".

That is, when the command laser output Ps is 4000 [W], the abnormality detection unit 51 determines that the decrease amount ΔP is equal to or greater than 200 [W] and less than 400 [W] as the first abnormal state. is 400 [W] or more and less than 3200 [W], it is determined as the second abnormal state, and if the decrease amount ΔP is 3200 [W] or more, it is determined as the third abnormal state.

In the above example, the abnormality detection unit 51 does not determine that the state is abnormal when the amount of decrease ΔP in the output is less than 200 [W]. 200 [W] corresponds to 5% of the command laser output Ps = 4000 [W]. cutting speed, etc.) are set. It should be noted that it is not essential to set the lower limit value of the decrease amount ΔP for determining an abnormal state to 5% of the command laser output Ps, and it may be set in consideration of the performance of the laser processing machine to which the gas laser device 100 is applied. .

In addition, the above ΔP = 200 [W], 400 [W], 3200 [W] means 5 [%], 10 [%], 80 [%] for Ps = 4000 [W] . Actually, the command laser output Ps is not limited to 4000 [W], and since it takes various values, the criterion is set by the ratio [%] as described above.

However, a plurality of abnormal states cannot be determined accurately only by setting the amount of decrease ΔP as described above. The reason is described below.

Normally, when the command laser output Ps is 4000 [W], the detected laser output Pk is also approximately 4000 [W]. In this case, the decrease amount ΔP (ΔP=Ps−Pk) of the detected laser output Pk with respect to the command laser output Ps is approximately 0 [W]. If some abnormality occurs, the detected laser output Pk decreases from 4000 [W] even though the command laser output Ps is 4000 [W], resulting in a decrease amount ΔP [W]. Here, it is assumed that the laser output suddenly decreases due to the abnormal discharge 7a during normal operation, and the detected laser output Pk changes from 4000 [W] to 150 [W]. Since the command laser output Ps remains at 4000 [W], the decrease amount ΔP of the detected laser output Pk with respect to the command laser output Ps is ΔP=Ps-Pk=4000-150=3850 [W]. I want to determine that it is the third abnormal state. However, the actual detected laser output Pk does not suddenly jump from 4000 [W] to 150 [W]. Since the power sensor that constitutes the output measurement unit 21 has a response time constant, the detected laser output Pk gradually decreases, for example, in the order of 4000→3900→3800→... and finally reaches 150 [W]. becomes. Therefore, the decrease amount ΔP first satisfies the criterion for determining the first abnormal state, that is, "200 [W] ≤ ΔP < 400 [W]", and after a short period of time, the second abnormal state is determined. The determination criterion, that is, "400 [W]≤ΔP<3200 [W]" is satisfied, and when more time elapses, the determination criterion that determines the third abnormal state, that is, "3200 [W]≤ΔP", is finally satisfied. . In other words, when determination is made using only the amount of decrease ΔP, the first abnormal state is always determined in the process in which ΔP gradually changes, and multiple types of abnormal states cannot be determined.

Therefore, in the present embodiment, timers T1 [s], T2 [s], and T3 [s] are added to the criteria corresponding to the first to third abnormal states, respectively, and these times is defined as 0≦T3<T2<T1. That is, the abnormality detection unit 51 determines that the first abnormal state occurs when the state in which the amount of decrease ΔP satisfies the criterion corresponding to the first abnormal state continues for T1. Similarly, when the state where the amount of decrease ΔP satisfies the determination criteria corresponding to the second abnormal state continues for T2 time, the abnormality detection unit 51 determines that the amount of decrease ΔP is the second abnormal state, and determines that the amount of decrease ΔP is the third abnormality. When the state satisfying the determination criteria corresponding to the abnormal state continues for T3 time, it is determined as the third abnormal state.

For example, when T3=0 [s], T2=1 [s], and T1=2 [s], the abnormality detection unit 51 determines that the third abnormality condition corresponding to the determination criterion "3200 [W]≤ΔP" is satisfied even for a moment, the third abnormal state is determined. In addition, when the criterion “400 [W]≦ΔP<3200 [W]” corresponding to the second abnormal state is continuously satisfied for T2=1 [s] or more, the abnormality detection unit 51 detects the second abnormal state. If the determination criterion "200 [W]≤ΔP<400 [W]" corresponding to the first abnormal state is continuously satisfied for T1=2 [s] or longer, the first abnormal state is determined.

Since the time constant of the decrease from 4000 [W] to 150 [W] due to the responsiveness of the power sensor is about 100 [ms], as described above, T2 = 1 [s] and T1 = 2 [s] By doing so, the abnormality detection unit 51 can determine the third abnormal state before determining the first abnormal state or the second abnormal state.

Incidentally, in practice, values such as T3=0.5 [s], T2=2 [s], and T1=3 [s] can be considered. This is because the detected laser output Pk changes from 0 [W] to 4000 [W] immediately after the start of oscillation when the gas laser device 100 is oscillated with a command laser output Ps of 4000 [W] from a state in which no laser is oscillated. ], there is a detection delay due to the responsiveness of the power sensor, and there is a decrease amount ΔP due to this. In order to prevent erroneous determination at this time, it is desirable to set T3=0.5 [s], which is longer than the time constant of the response of the power sensor, instead of T3=0 [s].

Next, operation of the gas laser device 100 will be described with reference to FIG. FIG. 9 is a flow chart showing an example of the operation of the gas laser device 100 according to the first embodiment. The flowchart of FIG. 9 shows an example of the operation of checking whether or not an abnormality has occurred after the gas laser device 100 has started to emit the laser beam 10, and taking measures against the occurrence of the abnormality. The operation shown in FIG. 9 is started, for example, after the gas laser device 100 is activated and the laser beam 10 is started to be emitted.

In the operation shown in FIG. 9, the abnormality detection unit 51 of the control device 15 first checks whether the gas laser device 100 satisfies "th1≦ΔP<th2" (step S11). Here, ΔP is the amount of decrease in the detected laser output Pk from the command laser output Ps described above. Further, th1 is the first threshold value and corresponds to the lower limit value of the range for determining the first abnormal state described above. th2 is a second threshold value and corresponds to the upper limit value of the range for determining the first abnormal state described above. Therefore, in step S11, the abnormality detection unit 51 confirms whether ΔP satisfies the criterion corresponding to the first abnormal state. Note that th2 is also the lower limit value of the range for determining the second abnormal state described above, and is the boundary between the range for determining the first abnormal state and the range for determining the second abnormal state.

When ΔP satisfies the criterion corresponding to the first abnormal state (step S11: Yes), the abnormality detection unit 51 confirms whether "T1<t1" holds (step S12). Here, T1 is the first time and corresponds to the timer T1 described above. t1 is the elapsed time after ΔP satisfies the criterion corresponding to the first abnormal state. If "T1<t1" does not hold (step S12: No), the abnormality detector 51 returns to step S11.

If "T1<t1" holds (step S12: Yes), the abnormality detection unit 51 determines that the output of the laser beam 10 has decreased due to the first abnormality, that is, the change in the composition of the laser medium 2, and The operation control unit 52 implements the first countermeasure (step S13). In the first measure, the emission of the laser beam 10 is stopped and the laser medium 2 inside the vacuum vessel 1 is replaced. That is, in step S13, the operation control unit 52 controls the power supply unit 6 and the vacuum pump 13 to stop the emission of the laser beam 10 and to replace the laser medium 2 in the vacuum vessel 1. . When the replacement of the laser medium 2 is completed, the operation control section 52 restarts the emission of the laser beam 10 .

When ΔP does not satisfy the criterion corresponding to the first abnormal state (step S11: No), the abnormality detection unit 51 confirms whether "th2≦ΔP<th3" holds (step S14). Here, th3 is the third threshold value and corresponds to the upper limit value of the range for determining the second abnormal state described above. Therefore, in step S14, the abnormality detection unit 51 confirms whether ΔP satisfies the criterion corresponding to the second abnormal state. Note that th3 is also the lower limit value of the range for determining the third abnormal state described above, and is the boundary between the range for determining the second abnormal state and the range for determining the third abnormal state.

When ΔP satisfies the criterion corresponding to the second abnormal state (step S14: Yes), the abnormality detection unit 51 confirms whether "T2<t2" holds (step S15). Here, T2 is the second time and corresponds to the timer T2 described above. t2 is the elapsed time after ΔP satisfies the criterion for the second abnormal state. If "T2<t2" does not hold (step S15: No), the abnormality detector 51 returns to step S11.

If “T2<t2” holds (step S15: Yes), the abnormality detection unit 51 detects the above-described second abnormal state, that is, occurrence of angular deviation of the optical resonator mirror, or burning of dust onto the mirror surface. , the operation control unit 52 determines that the output of the laser beam 10 has decreased, and performs the second countermeasure (step S16). In the second countermeasure, the emission of the laser beam 10 is stopped and a message prompting the user to resolve the abnormality is displayed. That is, in step S16, the operation control section 52 controls the power supply unit 6 to stop the emission of the laser beam 10, and causes the display section 53 to display a message prompting the user to resolve the abnormality.

When ΔP does not satisfy the criterion corresponding to the second abnormal state (step S14: No), the abnormality detection unit 51 confirms whether "th3≦ΔP" holds (step S17). In this step S17, the abnormality detection unit 51 confirms whether ΔP satisfies the criterion corresponding to the third abnormal state. When ΔP does not satisfy the criterion corresponding to the third abnormal state (step S17: No), the abnormality detection section 51 returns to step S11.

When ΔP satisfies the criterion corresponding to the third abnormal state (step S17: Yes), the abnormality detection unit 51 confirms whether "T3<t3" holds (step S18). Here, T3 is the third time and corresponds to the timer T3 described above. t3 is the elapsed time after ΔP satisfies the criterion corresponding to the third abnormal state. If "T3<t3" does not hold (step S18: No), the abnormality detector 51 returns to step S11.

If "T3<t3" holds (step S18: Yes), the abnormality detection unit 51 determines that the output of the laser beam 10 has decreased due to the third abnormality, that is, the occurrence of abnormal discharge, and controls the operation. The unit 52 implements the third handling (step S19). In the third countermeasure, the emission of the laser beam 10 is stopped, and the gas laser device 100 is shifted to a state in which the user's operation to restart the gas laser device 100 is not accepted. That is, in step S19, the operation control unit 52 controls the power supply unit 6 to stop the emission of the laser beam 10, and shifts to a state in which the operation to restart the gas laser device 100 is not accepted from the user.

As described above, in the gas laser device 100, the amount of decrease ΔP of the detected laser output Pk with respect to the command laser output Ps and the amount of decrease ΔP of the detected laser output Pk with respect to the command laser output Ps, and the elapsed times t1, t2, and t3 from when ΔP satisfies the judgment criteria for the abnormal state, respectively. Based on this, it is possible to detect multiple types of abnormalities and take appropriate measures based on the detection results.

Next, the hardware configuration of the control device 15 included in the gas laser device 100 will be described. FIG. 10 is a diagram showing an example of hardware that implements the control device 15 included in the gas laser device 100 according to the first embodiment. Control device 15 can be realized by processor 101, memory 102 and display 103 shown in FIG. An example of the processor 101 is a CPU (Central Processing Unit, processing unit, arithmetic unit, microprocessor, microcomputer, DSP (Digital Signal Processor)) or system LSI (Large Scale Integration). Examples of the memory 102 include RAM (Random Access Memory), ROM (Read Only Memory), non-volatile or volatile semiconductor memory such as flash memory, magnetic disk, and the like. An example of the display 103 is a liquid crystal display.

The abnormality detection unit 51 and the operation control unit 52 of the control device 15 are implemented by the processor 101 executing programs for operating as these units. A program for operating as the abnormality detection unit 51 and the operation control unit 52 is stored in advance in the memory 102 . The processor 101 operates as an abnormality detection unit 51 and an operation control unit 52 by reading out and executing programs from the memory 102 . Also, the display unit 53 is realized by the display device 103 .

As described above, in the gas laser device 100 according to the first embodiment, the controller 15 that controls the laser oscillator 20 that emits the laser beam 10 monitors the output of the laser beam 10, and based on the behavior of the output, Detect multiple types of abnormal conditions. Specifically, the abnormality detection unit 51 of the control device 15 detects the magnitude relationship between the decrease amount ΔP of the laser beam 10 and a plurality of threshold values (first threshold value, second threshold value, and third threshold value), and the magnitude relationship changes. A plurality of types of abnormal states (first abnormal state, second abnormal state, and third abnormal state) are detected based on the length of time that continues without interruption. According to the gas laser device 100 according to the first embodiment, it is possible to detect a plurality of types of abnormal states in which the output of the laser beam 10 is lowered while suppressing complication of the device configuration.

Further, since the gas laser device 100 can detect the first abnormal state in which the output of the laser light 10 is reduced due to a change in the composition of the laser medium 2, the laser medium 2 can be replaced at a timing corresponding to the change in the composition of the laser medium 2. It becomes possible to As a result, compared with the conventional configuration in which the laser medium is replaced at a predetermined sealing time, the frequency of replacing the laser medium can be reduced, the purchase cost of the laser medium 2 can be reduced, and the laser Downtime associated with media replacement can be reduced.

In addition, since the gas laser device 100 can detect the second abnormal state in which the output of the laser beam 10 is reduced due to the occurrence of angular misalignment of the optical resonator mirrors or the burning of dust onto the mirror surface, the problem is urged to be eliminated. A message can be sent to the user. For example, if the gas laser device 100 has a configuration in which the user can adjust the optical axis, the gas laser device 100 prompts the user to work by presenting a method of adjusting the optical axis to eliminate the angular deviation of the optical resonator mirrors. be able to. Also, if the gas laser device 100 has a configuration in which the user can replace the optical resonator mirror, the gas laser device 100 can prompt the user to replace the optical resonator mirror by presenting the method to the user. As a result, when the second abnormal state occurs, there is no need to separately request the service person to perform the work to restore the gas laser device 100, so that the cost required for restoration can be reduced and the time required for restoration can be reduced. can be shortened.

In addition, since the gas laser device 100 can detect the third abnormal state in which the output of the laser light 10 is reduced due to the occurrence of abnormal discharge, the emission of the laser light 10 is quickly stopped and the gas laser device 100 is restarted. can be shifted to a state where it is not accepted from the user. As a result, it is possible to prevent breakage of the glass or ceramic constituting the electrode 5 due to the abnormal discharge continuing for a long time or repeatedly occurring even for a short time.

In the present embodiment, a configuration for detecting three kinds of abnormal states from the amount of decrease in the output of laser light 10 has been described. , four or more types of abnormal states can be detected.

Embodiment 2.
A gas laser device according to a second embodiment will be described. The configuration of the gas laser device is the same as that of the first embodiment (see FIG. 1).

As described in Embodiment 1, the decrease in the output of the laser light 10 due to the composition change of the laser medium 2 is very slow, while the decrease in the output of the laser light 10 due to the angular displacement of the optical resonator mirrors, and , the output of the laser beam 10 is abruptly reduced due to dust burning onto the mirror surface. Therefore, the two can be separated by the rate of change of the decrease amount ΔP of the detected laser output Pk with respect to the command laser output Ps.

Therefore, the abnormality detection unit 51 of the control device 15 performs the following operations in addition to the operations described in the first embodiment. The abnormality detection unit 51 sets a speed threshold for separation with respect to the change speed of the decrease amount ΔP of the detected laser output Pk with respect to the command laser output Ps, and if the change speed is greater than the set speed threshold, the second , and if the speed change is equal to or less than the speed threshold, it is determined to be the first abnormal state. For example, when the determination in step S12 of the flowchart shown in FIG. 9 is "Yes", the abnormality detection unit 51 further compares the rate of change of the decrease amount ΔP of the detected laser output Pk with respect to the command laser output Ps with the speed threshold. If the change speed is equal to or less than the speed threshold value, it is determined as the first abnormal state, and step S13 (first countermeasure) is performed. On the other hand, if the change speed is not equal to or less than the speed threshold, the abnormality detection unit 51 returns to step S11 without executing step S13. Further, even when the determination in step S15 of the flowchart shown in FIG. If the change speed is greater than the speed threshold value, the second abnormal state is determined and step S16 (second countermeasure) is executed. On the other hand, if the change speed is not greater than the speed threshold, the abnormality detection unit 51 returns to step S11 without executing step S16.

As described above, in addition to the operation described in the first embodiment, the abnormality detection unit 51 performs the operation of determining an abnormal state in consideration of the change speed of the decrease amount ΔP of the detected laser output Pk with respect to the command laser output Ps. By doing so, it is possible to improve the determination accuracy of the abnormal state. The reason for this will be explained below.

As described in the first embodiment, when an external force is applied to the gas laser device 100 to shift the angle of the optical resonator mirror, the output of the laser beam 10 is reduced. At this time, the amount of angular deviation changes depending on the magnitude of the force applied from the outside, and the degree of reduction in the output of the laser beam 10 also changes. Therefore, in the first embodiment, the range of the amount of decrease in the output of the laser beam 10 when it is determined that the second abnormal state is due to the angular deviation of the optical resonator mirror or the burning of dust on the mirror surface is set to ΔP=400. It is covered by a large range of up to 3200 [W]. The inventor actually conducted experiments by changing various externally applied forces, but the output of the laser beam 10 did not significantly decrease beyond the range of ΔP = 400 to 3200 [W]. . Regarding the decrease in the output of the laser beam 10 due to dust burning onto the mirror surface, the larger the size of the dust burning onto the mirror surface, the larger the amount of reduction in the output of the laser beam 10. In such a case, some people may be concerned that they may not be able to make a good judgment. In other words, the output of the laser beam 10 is greatly reduced to such an extent that it exceeds the range of ΔP=400 to 3200 [W], and the third abnormal state described above (the range of the decrease amount ΔP of the output of the laser beam 10 is There may be a concern that it may be erroneously determined as an abnormal state of 3200 to 4000 [W]. However, according to the inventor's experience so far, there is no case in which the output of the laser beam 10 has decreased significantly beyond the above range of ΔP=400 to 3200 [W] due to dust burning onto the mirror surface. This is because, in the case of large dust particles, since the mass is large, the large dust particles may be blown up by the flow of the laser medium 2 circulated by the blower 3 as described in the first embodiment and reach the vicinity of the mirror surface. Because there is none. If the dust does not reach near the surface of the mirror, it will not stick to the mirror.

As described above, the decrease in the output of the laser beam 10 due to the angular misalignment of the optical resonator mirrors or the burn-in of dust on the mirror surface, which is the second abnormal condition, is erroneously determined as the third abnormal condition. However, on the other hand, when the force applied from the outside is small, and when very small dust particles stick to the mirror surface, the amount of decrease in the output of the laser beam 10 is small. In some cases, it may be erroneously determined to be the first abnormal state, that is, the decrease in the output of the laser light 10 due to the composition change of the laser medium 2 . As described in Embodiment 1, the range of the amount of decrease in the output of the laser beam 10 when the first abnormal state is determined is ΔP=200 to 400 [W], and the second abnormal state is determined. Since it is much smaller than the range (ΔP=400 to 3200 [W]) of the amount of decrease in the output of the laser beam 10 in the case, the probability of this misjudgment is small, but it is possible to completely eliminate this misjudgment. desirable.

Under these circumstances, in the second embodiment, attention is focused on the change speed of the decrease amount ΔP of the detected laser output Pk with respect to the command laser output Ps. The second abnormal state is determined, and the first abnormal state is determined when the speed change is equal to or less than the speed threshold. As a result, the accuracy of determining which of the first abnormal state and the second abnormal state applies is enhanced.

In each embodiment, an example in which carbon dioxide gas is used as the laser medium 2 has been described, but the laser medium 2 is not limited to carbon dioxide gas. Each embodiment also holds true when a gas other than carbon dioxide gas is used as the laser medium 2 .

The configurations shown in the above embodiments are only examples, and can be combined with other known techniques, or can be combined with other embodiments, without departing from the scope of the invention. It is also possible to omit or change part of the configuration.

1 vacuum vessel, 2 laser medium, 3 blower, 4 rectifying duct, 5 electrode, 6 power supply unit, 7 discharge, 7a abnormal discharge, 8 partial reflector, 9 total reflector, 10 laser light, 11 heat exchanger, 12 aperture , 13 vacuum pump, 14 cooling device, 15 control device, 20 laser oscillation section, 21 output measurement section, 51 abnormality detection section, 52 operation control section, 53 display section, 100 gas laser device.

Claims (2)

a laser oscillator that generates laser light using a gas as a laser medium;
The magnitude relationship between the amount of decrease in the output of the laser light emitted from the laser oscillation unit from the command output and each of the first threshold, the second threshold, and the third threshold, and the time during which the magnitude relationship continues without changing. an abnormality detection unit that detects a first abnormal state, a second abnormal state, and a third abnormal state of the laser oscillation unit based on the length;
with
The abnormality detection unit is
detecting a first abnormal state when the duration of the state in which the amount of decrease is equal to or greater than the first threshold and less than the second threshold exceeds a first time;
detecting a second abnormal state when the duration of the state in which the amount of decrease is equal to or greater than the second threshold and less than the third threshold exceeds a second time shorter than the first time;
detecting a third abnormal state when the duration of the state in which the amount of decrease is equal to or greater than the third threshold exceeds a third time shorter than the second time;
when the abnormality detection unit detects the first abnormal state, stopping the emission of the laser light, replacing the laser medium, and then restarting the emission of the laser light;
when the abnormality detection unit detects the second abnormal state, stopping the emission of the laser beam and displaying a message prompting a user to eliminate the abnormality on the display unit;
When the abnormality detection unit detects the third abnormal state, stop emitting the laser light and shift to a state in which a user's operation for instructing restart is not accepted.
A gas laser device characterized by: a laser oscillator that generates laser light using a gas as a laser medium;
The magnitude relationship between the amount of decrease in the output of the laser light emitted from the laser oscillation unit from the command output and each of the first threshold, the second threshold, and the third threshold, and the time during which the magnitude relationship continues without changing. an abnormality detection unit that detects a first abnormal state, a second abnormal state, and a third abnormal state of the laser oscillation unit based on the length;
with
The abnormality detection unit is
A first abnormal state is determined when the duration of the state in which the amount of decrease is greater than or equal to the first threshold value and less than the second threshold value exceeds a first time period and the rate of change of the amount of decrease is less than or equal to the speed threshold value. death,
If the duration of the state in which the amount of decrease is greater than or equal to the second threshold value and less than the third threshold value exceeds a second time period that is shorter than the first time period, and the speed of change is greater than the speed threshold value, a second 2 abnormal state,
determining a third abnormal state when the duration of the state in which the amount of decrease is equal to or greater than the third threshold exceeds a third time shorter than the second time;
when the abnormality detection unit detects the first abnormal state, stopping the emission of the laser light, replacing the laser medium, and then restarting the emission of the laser light;
when the abnormality detection unit detects the second abnormal state, stopping the emission of the laser light and displaying a message prompting a user to eliminate the abnormality on the display unit;
When the abnormality detection unit detects the third abnormal state, stop emitting the laser light and shift to a state in which a user's operation for instructing restart is not accepted.
A gas laser device characterized by:

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